Culprit? SurfShark VPN
Battle.net agent went to sleep. Attempting to wake it up…
Tried every single thing suggested: https://eu.battle.net/support/en/article/16531 but it still didn’t work.
What’s missing in the above suggestions is the possibility a VPN could cause problems. It didn’t occur to me to uninstall because it never caused problems before enabled or disabled.
Then it occurred to me that I changed some options to the VPN hours before launching battle.net. Resetting those options didn’t work but uninstalling the VPN did.
So for whom would have the above error or similar connection errors in the future, keep in mind that a VPN somehow is a security program too and just might cause problems.